Systems and methods for monitoring low speed of a rotorcraft

ABSTRACT

Systems and methods to provide alerts when a rotorcraft is in a low airspeed condition. During takeoff or go-around, an aural alert is provided to the pilot before the aircraft slows to less than the effective translational lift speed. The aural, visual, and/or tactile alert gets the pilot&#39;s attention to manage the aircraft&#39;s airspeed before it is too late in this critical flight phase.

BACKGROUND OF THE INVENTION

As the helicopter speed decreases below effective translational lift (ETL) speed, the rotor efficiency becomes less effective. In many helicopter accidents, pilots get disoriented, and often drop the helicopter's speed after takeoff or during a go-around, without noticing it. In a lot of cases, this insidious slow loss of airspeed is not detected by the pilots and results in a loss of performance, leading to a crash.

SUMMARY OF THE INVENTION

During takeoff or go-around an aural alert is provided to the pilot before the aircraft slows to less than the effective translational lift speed. The aural and/or visual alert gets the pilot's attention to manage the aircraft's airspeed before it is too late in this critical flight phase.

This new airspeed monitor can be implemented in the helicopter's enhanced ground-proximity warning system (EGPWS). The helicopter's EGPWS currently consumes all of the aircraft's sensors required to perform the function and currently provides aural alerts in the cockpit. The monitor would be enabled after takeoff or go-around, after the aircraft has reached a predetermined speed and the aircraft is less than a predetermined height, and would then provide an alert, when computed airspeed decreases to below a predetermined speed (a value just above the effective translational lift speed). The alert is provided sooner when the engine(s) is operating at high torque setting.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred and alternative embodiments of the present invention are described in detail below, with reference to the following drawings:

FIG. 1 is a block diagram of an exemplary system formed in accordance with an embodiment of the present invention;

FIG. 2 is a flow diagram of an exemplary method performed by the system shown in FIG. 1; and

FIG. 3 is an exemplary rotorcraft torque-versus-speed graph.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an exemplary rotorcraft (i.e., helicopter) 20 that includes a system 22 for alerting a rotary aircraft (i.e., helicopter) of a situation in which its airspeed drops below an acceptable level, in a situation where aircraft lift is compromised, for example, takeoff and a missed-approach go-around situation. The system 22 includes a processor 24 that is in signal communication with an engine sensor(s) 28, an autopilot system 30, an air data computer (ADC) 32, as well as various other avionic components (e.g., flight management system (FMS)). The processor 24 analyzes the information from the engine sensor(s) 28, the autopilot system 30, and the ADC 32 in order to determine whether the helicopter 20 has adequate speed in order to meet certain lift requirements needed for the situation that the helicopter 20 is currently in.

FIG. 2 illustrates an exemplary process 60 performed by the system 22. First, at a block 64, the processor 24 receives rate-of-altitude change information from the ADC 32. Next, at a block 66, the processor 24 receives engine torque information from the engine sensor(s) 28. Then, at a block 68, the processor 24 receives autopilot status information from the autopilot system 30. The step performed at block 68 is optional, depending upon the amount of functionality desired for the system 22. The order of the steps may vary.

At a first decision block 70, the processor 24 determines intent of the helicopter 20, based on the received information. Intent may mean what the helicopter 20 is going to do or is currently doing. If the received information does not indicate intent of the helicopter 20 to be a takeoff or a go-around situation, then the process 60 returns to the beginning at block 64. If the intent is determined by the processor 24 to be a takeoff or a go-around situation, then, at a decision block 72, the processor 24 determines if the current airspeed, as generated by the ADC 32 is less than a predefined best rate-of-climb speed (V_(broc)), by a predefined threshold amount. If the processor 24 determines that the airspeed is not less than the V_(broc) by the threshold amount, then the process 60 returns to the beginning at block 64. If the processor 24 determines that the airspeed is less than the V_(broc) by the threshold amount, then the processor 24 determines, at a decision block 76, whether the current airspeed is not accelerating greater than a first threshold acceleration amount and the airspeed is not decelerating greater than a second threshold acceleration amount. If the processor 24 determines that the condition at decision block 76 is true, the processor 24 generates a first low-speed alert 78. However, if the airspeed does not meet the conditions set out in decision block 76, then the processor 24 determines if the airspeed is decelerating greater than the second threshold acceleration amount, as shown in decision block 80. If the airspeed is decelerating greater than the second threshold amount, then the processor 24 generates a second low-speed alert, at block 82. If, however, the airspeed is not decelerating greater than the second threshold acceleration amount, the process 60 returns to the beginning at block 64.

FIG. 3 shows an exemplary graph 90 of torque-versus-airspeed for an exemplary helicopter. In one embodiment, an alert is outputted when the current airspeed is below the best rate-of-climb speed V_(broc). Arrow 92 indicates the situation in which, when the airspeed is below V_(broc), the airspeed is decelerating greater than the second threshold amount. The arrow 94 indicates the situation also below the V_(broc) in which the airspeed is not accelerating greater than a first threshold amount and the airspeed is not decelerating greater than the second threshold amount. Thus, just because the airspeed is below the V_(broc), an alert will not be presented to the flightcrew unless the acceleration situations, according to the process 60, are met. The generated first and second low-airspeed alerts are sent to the output device 38 for presentation to the flightcrew. Examples of the output device 38 include speakers, a display device, and/or a tactile feedback component.

While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow. 

The embodiments of the invention, in which an exclusive property or privilege is claimed, are defined as follows:
 1. A method comprising: at a processing device, receiving vehicle position and airspeed information; determining if operation intent of vehicle meets at least one predefined criterion based on the received vehicle position and airspeed information; and if the intent meets the at least one predefined criterion, generating a first low-speed alert if airspeed is less than a predetermined speed by a threshold amount and an acceleration value is between a first and second acceleration value.
 2. The method of claim 1, wherein the predetermined speed comprises a best rate-of-climb speed (V_(broc)).
 3. The method of claim 1, wherein if the intent meets the at least one predefined criterion based on the received vehicle position and airspeed information, generating a second speed alert if the acceleration value is less than the second acceleration value.
 4. The method of claim 1, further comprising at the processing device, receiving autopilot status information; and determining if operation intent of vehicle meets at least one predefined criterion, further based on the received autopilot status information.
 5. The method of claim 1, further comprising at the processing device, receiving engine torque information; and determining if operation intent of vehicle meets at least one predefined criterion further based on the received engine torque information.
 6. A system located in a vehicle, the system comprising: a means for receiving vehicle position and airspeed information; a means for determining if operation intent of vehicle meets at least one predefined criterion, based on the received vehicle position and airspeed information; and if the intent meets the at least one predefined criterion, a means for generating a first low-speed alert if airspeed is less than a predetermined speed by a threshold amount and an acceleration value is between a first and second acceleration value.
 7. The system of claim 6, wherein the predetermined speed comprises a best rate-of-climb speed (V_(b).).
 8. The system of claim 6, further comprising a means for generating a second speed alert if the acceleration value is less than the second acceleration value, if the intent meets the at least one predefined criterion, based on the received vehicle position and airspeed information.
 9. The system of claim 6, further comprising: a means for receiving autopilot status information; and a means for determining if operation intent of the vehicle meets at least one predefined criterion, further based on the received autopilot status information.
 10. The system of claim 6, further comprising: a means for determining engine torque information; and a means for determining if operation intent of the vehicle meets at least one predefined criterion, further based on the determined engine torque information.
 11. A system located in a vehicle, the system comprising: a position and speed sensor configured to determine vehicle position and airspeed information; a processing device configured to determine if operation intent of the vehicle meets at least one predefined criterion based on the received vehicle position and airspeed information; and if the intent meets the at least one predefined criterion, generate a first low-speed alert if airspeed is less than a predetermined speed by a threshold amount and an acceleration value is between a first and second acceleration value.
 12. The system of claim 11, wherein the predetermined speed comprises a best rate-of-climb speed (V_(broc)).
 13. The system of claim 11, wherein the processing device is further configured to generate a second speed alert if the acceleration value is less than the second acceleration value, if the intent meets the at least one predefined criterion, based on the received vehicle position and airspeed information.
 14. The system of claim 11, further comprising: an autopilot system configured to generate autopilot status information, wherein the processing device is further configured to determine if operation intent of the vehicle meets at least one predefined criterion, further based on the generated autopilot status information.
 15. The system of claim 11, further comprising: an engine sensor configured to determine engine torque information; and wherein the processing device is further configured to determine if operation intent of vehicle meets at least one predefined criterion, further based on the determined engine torque information. 